X-ray diffraction study revealing phase coexistence in barium titanate stannate

In this paper, the results of a temperature dependent x-ray diffraction (XRD) study on BaTi_0.95Sn_0.05O₃ (BTS-5) ceramics are compared with dielectric measurements. The orthorhombic-tetragonal phase transition at T₂ = 306 K is found to proceed in a considerably wider temperature range than expected from the dielectric anomaly. Although the macroscopic properties of BTS-5 indicate a rather sharp ferroelectric phase transition at T_c = 358K, we observe anomalous XRD-patterns in a 25 K wide temperature range. This is interpreted in terms of mechanically clamped tetragonal and cubic phase, coexisting in the vicinity of T_c in grains with inhomogeneous Sn-distribution.